A new generation of non-rotational electromagnetic transducers have recently become available for portable communications devices, such as pagers, for operation as tactile alerting devices. The new generation of non-rotational electromagnetic transducers have significantly reduced the energy consumed by the transducers and have significantly reduced the audible sound level developed when the transducer is in actual operation as compared to the prior motor counterweight mechanisms. The gains achieved have not been without a compromise in the circuitry required to drive the non-rotational electromagnetic transducers. Because the non-rotational electromagnetic transducers utilize non-linear spring members, the transducers have generally required external drive circuits to generate a swept frequency driving signal to maximize their output during operation. While these external drive circuits have proved very useful in maximizing the output of the non-rotational electromagnetic transducers, they at best, have only approximated the natural mechanical system response of the transducers.
The requirement for external drive circuits have been largely overcome in electromagnetic vibrator devices previously utilized in power supplies in certain radio applications which have utilized a linear resilient reed, an electromagnet, and a pair of rigid interrupter contacts in association with a step-up transformer. When the electromagnetic vibrator device was connected to a storage battery, power was obtained by interrupting the current passing from the battery through the primary of the transformer. Such electromagnetic vibrator devices made and reversed the current supplied to the primary of the transformer by interrupting the current at regular intervals with the pair of interrupter contacts and reversing the voltage applied to the primary of the transformer which resulted in generating an alternating magnetic field which induced a stepped-up voltage in the secondary of the transformer. Automobile horns and door-bell buzzers are examples of other such self interrupting devices. It will be appreciated that all of these devices have utilized linear resilient reeds such as flexible cantilever beams or diaphragms as the contact elements which connect to rigid contactor elements, making these devices operational at only a single frequency dependent upon the external circuit elements to which the electromagnetic vibrator devices were attached.
What is needed is an, apparatus for driving a non-rotational electromagnetic transducer which does not require a complex external driving circuit. What is also needed is an apparatus for self-exciting the non-rotational electromagnetic transducer in a manner which relies not on the external circuit elements, but rather on the natural response of the non-rotational electromagnetic transducer. Furthermore, what is needed is an apparatus for driving the non-rotational electromagnetic transducer which utilizes the natural mechanical system response of the non-rotational electromagnetic transducer to maximize the tactile output of the non-rotational electromagnetic transducer over the non-linear operating range of the non-rotational electromagnetic transducer. And furthermore, what is needed is an apparatus for self exciting the non-rotational electromagnetic transducer which results in a frequency of operation to be swept dynamically in response to the natural response of the non-rotational electromagnetic transducer, thereby resulting in a tactile energy output to be maximized.